GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2005 🢒 Grand Prix 🢒 Accessories 🢒 Navigation Systems 🢒 DTC P0506

Circuit Description

The throttle actuator (TAC) motor is controlled by the TAC module using various inputs from the powertrain control module (PCM) which are communicated across serial data. The DC motor located on the throttle body drives the throttle plate. In order to decrease idle speed, the TAC module commands the throttle closed, reducing air flow into the engine. In order to increase idle speed, the TAC module commands the throttle plate open, allowing more air to pass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, DTC P0506 sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0506 Idle Speed Low

Conditions for Running the DTC
    • DTCs P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125, P0128, P0171, P0172, P0201-P0206, P0220, P0300, P0401, P0404, P0405, P0443, P0496, P0502, P0503, P1106, P1107, P1111, P1112, P1114, P1115, P1125, P1404, P1516, P2101, P2107, P2108, P2119, P2120, P2125, P2135, P2138, and U0107 are not set.
    • DTCs P0136, P0401, and P0420 have passed.
    • The engine is operating.
    • The engine coolant temperature (ECT) is more than -40°C (-40°F).
    • The intake air temperature (IAT) is more than -40°C (-40°F).
    • The barometric pressure (BARO) is more than 60 kPa.
    • The system voltage is between 11-18 volts.
    • The vehicle speed is less than 4.8 km/h (3 mph).
    • The throttle position (TP) angle is less than 0.25 percent.

Conditions for Setting the DTC
    • The difference between the actual and desired idle RPM exceeds a calibrated limit. This limit varies from 300 RPM at -40°C (-40°F) to 100 RPM at 152°C (305°F) based on engine coolant temperature.
    • The above conditions are present for 8 seconds in order for the test to fail. Four tests must fail in order to set this DTC. The vehicle must exit conditions for running between each test.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Test Description

The number below refers to the step number in the diagnostic table.

  1. This test determines whether the engine can achieve the commanded RPM. If the engine does not reach the commanded RPM, the test determines whether the RPM is too high or too low.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Powertrain Control Module Connector End Views and Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Start the engine.
  2. Ensure the engine is at operating temperature.
  3. Command the engine speed to 1,500 RPM, then to 500 RPM, and back to 1,500 RPM with a scan tool.
  4. Exit the RPM control function.

Does the engine speed correspond, within 100 RPM, with each command?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Inspect for any condition that can reduce idle speed by increasing engine load. The following examples are possible conditions:

    • Incorrect torque converter clutch (TCC) operation
    • Accessories that require additional torque to operate
    • Restricted exhaust
    • Mechanical conditions that limit engine speed

Did you complete the action?

Go to Step 4

--

4
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 5

5

Important: Be aware that repairing 1 individual condition may correct more than 1 DTC.

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK